MULTIPLE ARRESTED SYNTHETIC APERTURE RADAR

A Multiple Arrested Synthetic Aperture Radar (MASAR) for the detection of slowly moving targets in clutter is analytically conceptualized and evaluated. The radar consists of a succession of synthetic aperture antennas which are coincident in space but are displaced in time by several interpulse periods. The radar is evaluated using the target to clutter power ratio as the measure of performance. The radar is assumed to be clutter power limited, so noise is ignored in the evaluation. The evaluation consists of a comparison between three different receiver processing schemes. The first processor is a set of weights which optimizes the target to clutter power ratio and is the central feature of MASAR. The second processor is a set of weights comprising the target signal, itself; it can be construed as a "smart, ad hoc" design and is shown to be optimum for rapidly decorrelating clutter. The third processor is set of binomial weights; effectively, it reduces the system to an n-pulse canceller which, for a two antenna system, is the well known Displaced Phase Center Antenna (DPCA) radar.; In order to perform the analysis, a generalized signal return is formulated with which closed form expressions for the target signal and the clutter cross-power correlation are derived. This generalized signal return is a range-amplitude, radiation pattern weighted integration of the electric field backscattering coefficient over the backscattering region. Both the target and the clutter are modeled with the electric field backscattering coefficient: deterministically for the target, stochastically for the clutter.; The target is modeled simply as a deterministically moving point scatter with the same albedo as a point of clutter.; The clutter is modeled as a homogeneous, isotropic, two-dimensional, spatiotemporal random field. This random field represents the amplitude and phase of the electric field backscattering coefficient as a function of time for every point in the scattering region observed from positions along the MASAR flight path. Only the correlation properties of this random field are required for the analysis.; The analysis is three-fold and considers targets moving between zero and 60 miles per hour at all track angles. First, the improvement of MASAR with the optimum processor is considered relative to that with the target and the binomial processors. Second, the response of each processor to off-boresight targets is considered. Third, the response of the optimum processor to other targets on the boresight is examined.; The analysis shows that MASAR with optimum receiver weights, generating four synthetic apertures each three feet long, can extract a three mile per hour target at ten miles from slowly decorrelating clutter 45 dB better than MASAR with target weights and over 144 dB better than MASAR with binomial weights. For a 60 mile per hour target, under the same circumstances, the corresponding figures are 70 dB and 106 dB. The analysis further shows that, with longer synthetic apertures, both the target's location and velocity component parallel to the MASAR boresight can be accurately determined.; The conclusion is that MASAR, with its optimum weighting scheme, is a promising synthetic aperture radar concept for the detection of slowly moving targets immersed in strong clutter environments.